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APSUSC-17597; No of Pages 9

Synthesis and characterization of nano-sized nickel catalyst supportedon SiO2–Al2O3

Islam Hamdy Abd El Maksod a,*, Eman Z. Hegazy a, Sayed H. Kenawy b, Tamer S. Saleh c

a Physical Chemistry Department, National Research Centre Dokki, El Behouth Street, Dokki, Cairo, Egyptb Ceramic Department, National Research Centre Dokki, El Behouth Street, Dokki, Cairo, Egyptc Green Chemistry Department, National Research Centre Dokki, El Behouth Street, Dokki, Cairo, Egypt

1. Introduction

Nickel metal catalyst loaded on SiO2 or Al2O3 catalyst has beenused in hydrogenation reactions only as separate oxides [1–8].However, to our knowledge the catalytic behavior of metallic nickelloaded on mixed SiO2–Al2O3 solid has not been yet investigated.

The present work aimed at shedding more light upon the effectof the degree of the crystallinity of SiO2–Al2O3 support on thecatalytic activity of nickel catalyst. The reaction used in this studywas the hydrogenation of p-nitrophenol into p-aminophenol.

p-Aminophenol is considered to be very important intermediatein the manufacture of many analgesic and antipyretic drugs, such asparacetamol, acetanilide, phentacin, . . . etc. [9–15]. It is also used as adeveloper in photography (under trade names of activol or azol), inaddition of its use in chemical dye industries [16].

There are several methods used in the preparation of p-aminophenol from p-nitrophenol such as: (1) metal/acid reduction[17], (2) catalytic hydrogenation [18], (3) electrolytic reduction[19], (4) homogeneous catalytic transfer hydrogenation [20], and(5) heterogeneous catalytic transfer hydrogenation, etc.

Among all previously mentioned methods, direct catalhydrogenation of p-nitrophenol to p-aminophenol becomesmost important one. This is because it could be an efficient rofor synthesis [15]. Raney nickel [21], nano-sized nickel [22]several noble metal catalysts, such as Pd/C [15], have been usecatalysts for this reaction. Due to their lowest cost and higcatalytic activity, supported nickel catalysts, are widely usedsuch reactions [15–21].

Although nickel catalyst is used in hydrogenation reacti[23–29], only few recent researches have been carried outhydrogenation of p-nitrophenol over nano-sized supported nimetal catalyst [10,30,31].

The present investigation reports the results of an intenstudy on preparation and characterization of nano-sized metanickel supported on SiO2–Al2O3 being prepared by sol–gelcalcined at 500–1500 8C. The techniques employed were XSEM, EDX, ESR and hydrogenation of p-nitrophenol

2. Experimental

Applied Surface Science xxx (2008) xxx–xxx

A R T I C L E I N F O

Article history:

Received 17 April 2008

Received in revised form 16 July 2008

Accepted 19 July 2008

Available online xxx

Keywords:

SiO2–Al2O3 support

Nickel catalyst

Catalytic activity

XRD

SEM

EDX

ESR

A B S T R A C T

SiO2–Al2O3 support material was prepared by sol–gel method, followed by calcination at 500, 1000

1500 8C. The supported nickel catalyst containing 5 wt% was obtained by impregnating a known ma

the calcined support material with nickel sulfate solution followed by drying and reduction w

hydrazine hydrate at 80–100 8C. The prepared catalysts were fully characterized by XRD and SEM,

and ESR. The hydrogenation of p-nitrophenol into p-aminophenol was performed using hydra

hydrate as hydrogen donor. The product of the reaction was examined using IR, and NMR. The res

showed that the degree of crystallinity of the support affects the catalytic activity of nano-size

catalyst. It was observed that as the degree of crystallinity of the support material increases the cata

activity increases. On the other hand, intermolecular interaction between nano-nickel clus

disappears completely in samples whose support was calcined at 1500 8C.

Crown Copyright � 2008 Published by Elsevier B.V. All rights reser

Contents lists available at ScienceDirect

Applied Surface Science

journa l homepage: www.e lsev ier .com/ locate /apsusc

ratecial

* Corresponding author. Tel.: +20 237346470.

E-mail address: [email protected] (Maksod).

Please cite this article in press as: I.H.A.E. Maksod, et al., Synthesis anAl2O3, Appl. Surf. Sci. (2008), doi:10.1016/j.apsusc.2008.07.117

0169-4332/$ – see front matter . Crown Copyright � 2008 Published by Elsevier B.V.

doi:10.1016/j.apsusc.2008.07.117

2.1. Materials

Tetraetoxysilane (TEOS; Fluka, >98% purity), aluminum nitnonahydrate (Al(NO3)3�9H2O), NiSO4�7H2O (Merck), Commer

d characterization of nano-sized nickel catalyst supported on SiO2–

All rights reserved.

mailto:[email protected]

http://dx.doi.org/10.1016/j.apsusc.2008.07.117

http://www.sciencedirect.com/science/journal/01694332


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y Nickel (Merck), Hydrazine hydrate 80% (Merck), p-nitro-ol (PNP) (Merck) and p-aminophenol (PAP) (as a standard

erials), Methanol (spectroscopic grade) (merck).

. Preparation of SiO2–Al2O3 mixed oxide support

iO2–Al2O3 mixed oxide support material was prepared by agel technique. A 2SiO2:3Al2O3 molar ratio batch of the supportprepared by slow hydrolysis. After gelling and drying the

ple was calcined at 500 8C for 2 h in order to remove theual nitrates and volatiles. The resulted solid is nominated as

500). The sample was then milled using agate mortars anded at 1000 and 1500 8C for 4 h. The resulted solids areinated as (SA-1000, and SA-1500) respectively. The surfaceof the prepared supports were 50, 20 and 10 m2/g for theorts SA-500, SA-1000, and SA-1500 respectively.

. Preparation of nano-sized nickel catalyst

ickel was loaded on support being calcined at 500, 1000 and0 8C; by means of impregnation. The extent of Ni was fixed at%. Reduction was done using hydrazine hydrate in an alkalineium at 80–100 8C in order to obtain the metallic form ofel.

Techniques

. Hydrogenation process

atalytic hydrogenation reaction was done by dissolving p-phenol in an appropriate amount of methanol, followed bytion of hydrazine hydrate as hydrogen source, then heating atC. The catalyst was added to the heated solution and the timeach 100% conversion was taken as an express of the catalyticity. The catalyst:reactant (PNP) was fixed at 1:5 molar ratio.he filtrate was then taken and evaporated at reduced pressurethe residue was recrystallized from hot water to give pureuct of PAP in almost 100% yield. The characteristics of theuct are listed below:

: (ymax/cm�1): 3423, 3340 (NH2), 3190 (OH).NMR DMSO-d6, d (ppm): 5.98 (s, 1H, OH, D2O-exchangeable),2 (d, 2H, J = 6.7 Hz, ArHs), 6.99 (d, 2H, J = 6.7 Hz, ArHs), 9.86

r s, 2H, NH2, D2O-exchangeable).

. X-ray diffraction (XRD)

-ray diffractograms of various solids were collected usinger D8 advance instrument with Cu Ka1 target with secondlyochromator 40 kV, 40 mA.

. ESR spectroscopy

SR spectra of different solids were measured usingcker Elexsys. 500) operated at X-band frequency. Thewing parameters are generalized to all samples otherwisetioned in the text. Microwave frequency: 9.73 GHz, receiver: 20, sweep width: 6000 center at 3480, microwave power:202637.

. Infrared spectroscopy

he infrared spectra were recorded in potassium bromide disksadzu FT IR 8101 PC infrared spectrophotometers.

2.2.6. SEM and EDX analysis

Images of scanning electron microscope (SEM) differentsamples and EDX analysis was performed using instrument‘‘JXA-840 A Ellectron probe Micro Analyzer-Japan’’.

2.2.7. Surface area measurements

The surface areas were measured using Quantachrome HighSpeed Gas Adsorption Nova 2000 instrument at 77 K.

3. Results and discussion

Hydrogenation of p-nitrophenol into p-aminophenol wasperformed on 5 Ni wt% catalyst, supported on the precalcinedsupports; SA-500, SA-1000 and SA-1500. The reaction follows thefollowing equation:

The hydrazine in the previous reaction acts as hydrogen donor.In addition, supported nickel catalyst acts as a bifunctionalcatalyst. Thus it firstly, decomposes hydrazine into H2 and N2.Furthermore, the nickel acts as a catalyst for the hydrogenation ofp-nitrophenol using the nascent hydrogen produced from previousstep.

During the hydrogenation process, the change in color wasobserved. Thus, a change from yellow color of PNP into green color(intermediate A) was firstly observed. After that, a discharge of allcolors (PAP) was occurred, accompanied with 100% conversion.The mechanism of this reaction is shown in Scheme 1.

The above mechanism enables us to follow the reaction by aself-change in color. This make us to believe in that, the express ofthe catalytic activity as the time to reach 100% conversion may bethe best choice for this reaction.

The supported catalysts were characterized by XRD, SEM, EDX,ESR and measuring the catalytic activity.

I.H.A.E. Maksod et al. / Applied Surface Science xxx (2008) xxx–xxx

Scheme 1.

. NMR analysis

he NMR spectra were recorded on a Varian Mercury VX-300spectrometer. 1H spectra were run at 300 MHz in deuterated

ethyl sulphoxide (DMSO-d6). Chemical shifts were related toof the solvent.

ase cite this article in press as: I.H.A.E. Maksod, et al., Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–

2O3, Appl. Surf. Sci. (2008), doi:10.1016/j.apsusc.2008.07.117


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3.1. XRD investigation of different solids

XRD diffractograms were used to follow up the crystallinephases of SiO2–Al2O3 support. Fig. 1 shows the diffractograms of5 Ni wt% loaded on SA-500, SA-1000 and SA-1500 supportsrespectively. It is seen from this figure, that, the support material

precalcined at 500 and 1000 8C, consists of poorly crystallialuminas, together with the main diffraction line of metallic nicHowever, the diffractogram of the nickel catalyst loaded osupport precalcined at 1500 8C consists of well crystallized a-Al(corrundom), SiO2 (crystobalite), SiO2–Al2O3 (mullite) and metanickel.

Fig. 2 depicts the XRD diffractograms of 5 Ni wt%-cataloaded on SA-500, SA-1000, and SA-1500, before and after sevsuccessive uses in hydrogenation of p-nitrophenol. Fromfigure, it can be observed that, a crystalline Ni metal phasdetected in all freshly prepared catalysts (showed by dashed liThe relative intensity of metallic nickel phase decreases progsively as the number of uses increases. This finding may indicthat, the crystalline nickel metal phase looses its degreecrystallinity via partial transformation into an amorphous phduring the hydrogenation reaction. In case of SA-1500 sampldecrease in the degree of crystallinity of both crystalline nickelother crystalline phases (crystobalite, corrundom, and mulwas observed after successive uses of catalyst several times.

3.2. SEM and EDX results

Fig. 3 represents the images of 5 Ni wt% fresh catalyst loadedSA-500 and after 5 times of use in catalytic hydrogenation of PN80 8C. From this figure, it can be observed that, only socrystallites of alumina phases existed in the SEM images, as beevidenced by EDX analysis (Table 1) and XRD (Fig. 1).

Fig. 1. XRD diffractograms of 5 Ni wt% on SA-500, SA-1000 and SA-1500, where 1,

crystobalite; 2, corrundom; 3, mullite; *g-Al2O3.


Fig. 2. XRD diffractograms of 5 wt% Ni load on SA-500, SA-1000 and SA-1500 supports before and after several times of successive using in hydrogenation of p-nitrohenol.

Please cite this article in press as: I.H.A.E. Maksod, et al., Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–Al2O3, Appl. Surf. Sci. (2008), doi:10.1016/j.apsusc.2008.07.117


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oreover, after 5 times of use, aggregation of the catalyst wasrved, which is much clear at lower magnification. The EDXysis (Table 1) for this sample was taken for two differenttions. The first position showed only the presence Al and Os, indicating the presence of Al2O3, while the second positioned the presence of Si, Al and O, which is indicative for the

ence of precursors of aluminosilicates.n addition, the Si and Al surface concentration, in the secondtion of the fresh catalyst, are much close to the calculated bulkes [Siexp, 9 atom%; Sical, 9, Alexp, 33 atom%; Alcal, 28 atom%]. Onother hand, the Ni surface concentration is much bigger than

of calculated bulk value by 82% [Niexp, 10 atom%, Nical,m%]. The previous remark indicates that the impregnation

hod increases the surface atom % of Ni. This finding is expectedolid samples prepared by wet impregnation method.

Fig. 4 shows the images of 5 Ni wt% fresh catalyst loaded on SA-1000 and after 5 times of use in hydrogenation of PNP. From thisfigure, it can be observed that, some crystallites are beginning to beformed. Moreover, the aggregation of the catalyst after 5 times ofsuccessive use was also observed, and this is accompanied by thedisappearance of the crystalline shapes. Moreover, EDX analysis ofthis sample (Table 1) showed that, there is an effective migration ofNi from the surface to the bulk by successive use (4! 1 atomic%).This process is accompanied also by a migration of some Si frombulk to the surface, while, Al and O remained almost unchanged. Itcan be also observed that, the surface atom concentration of Si, Al,O and Ni atoms are much closer to the calculated bulk values after5 times of successive use, which may affect the specific catalyticactivity of this catalyst as will be seen in the section of catalyticactivity.

Fig. 5 represents the images of 5 Ni wt% fresh catalyst loaded onSA-1500 and after 5 times of use, compared with bare supportsample. From this graph one can observe the clear formation ofhighly crystalline forms of the support. The aggregation of thecatalyst particles after several times of use is also observed here.The EDX analysis showed that the Ni migrates completely from thesurface to the bulk (5!�0.0 atomic%), while a high migration of Sifrom bulk to the surface is observed (5! 31 atomic%). The Alatoms migrate also, but this time from surface to bulk(39! 19 atomic%). These findings may be explained by, assumingthe collapse of the crystalline forms of the support which was

Fig. 3. SEM images of 5 Ni wt% supported on SA-500: (a) freshly prepared and (b) after 5 times of successive using in hydrogenation reaction.

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ase cite this article in press as: I.H.A.E. Maksod, et al., Synthesis an


confirmed formerly by XRD.From the previous observations the following remarks may be

drawn:

(i) For the fresh catalyst sample, the surface concentration of

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atomic% respectively. These values are closer to the calculatedvalues of loaded Ni (2 atom%), comparing with the highvalue of surface Ni concentration (10 atom%) loaded on SA-500. This means that the Ni atoms are not equally distributed

between surface and bulk, and are much higher concentraon the surface. This may be explained assuming thatinteraction between Ni atoms and the amorphous suppohigher than that of crystalline one. In other words, as

Fig. 4. SEM images of 5 Ni wt% loaded on SA-1000: (a) freshly prepared and (b) after 5 times of successive using in hydrogenation reaction.


Fig. 5. SEM images of bare support SA-1500: (a) freshly prepared 5% Ni wt%-SA-1500 and (b) after 5 times of successive using in hydrogenation reaction.



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degree of crystallinity of the support increases the interactionbetween Ni and the support decreases which was formerlyobserved from XRD and SEM results.It can be generally observed that, as the calcination of thesupport increases, the distribution of surface Si and Al deviatedfrom the calculated bulk values. As a consequence ofsuccessive use of the catalyst, a migration of both Si and Al,and even O occurs. The migrating atoms concentrations werefound to be much closer to the calculated bulk values. Thisleads us to conclude that, as the catalyst is being used, thecrystallinity of the support is being affected, i.e. the supporttransforms into amorphous phase.After successive use of the catalyst several times, theconcentration of the surface nickel atoms decreases. Thisdecrease is inversely proportional to the calcination tempera-ture, reaching to minimum at 1500 8C (nearly no nickelobserved at EDX analysis). It was suggested that, as the degreeof crystallinity of the support increases, the collapse of thecrystals during the successive use of the catalyst increases.This leads to a migration of the nickel species inside the bulk.

Fig. 6. Surface Ni atom% of catalyst after 5 times using against calcination

temperature.


. ESR spectra of different samples of 5% Ni loaded on SA-500, SA-1000 and SA-1500 8C as freshly prepared catalysts and after successive times of using. The dimensions

in the figures are driven from Eq. (1).

ase cite this article in press as: I.H.A.E. Maksod, et al., Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–



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Thus, the Ni mobility is directly proportional to the degree ofthe crystallinity of the support as can be drawn from Fig. 6.

4. ESR investigation of different catalyst samples

ESR technique is usually used to characterize the paramagneticcenters in the sample where a free electron exists. Although thistechnique can characterize effectively paramagnetic species ofmetal particle, it has a special interest when these particlesdiminished to a nano-scale, such as in our case, where nano-sizedmetal particles are existed.

Moreover, Kawabata [32] demonstrated his famous relationhypothesizing that the broadening of ESR signal of nano-metalparticles are suffering from quantum size effect and can becorrelated to the size of the nano-metal particle.

Accordingly, direct relationship between the line width DHpp

(or peak to peak width) of the signal of nano-particle in ESR spectraand its particle size are given in the following relation:

d ¼ a �DHppÞ0:5 (1)

where d is the particle size in nm, DHpp is the line width of ESRsignal in mT and a is the proportionality constant.

The proportionality constant ‘‘a’’ for our case nickel metal wasfound to be 1.2 [8]. This relation enables us to estimate correctlythe average particle size of nickel even it is not existed incrystalline form. Thus, Fig. 7 represents the ESR spectra ofsamples under investigation under different calcination tem-peratures and after successive times of use. From these spectraone can observe that the characteristic signal of nickel metalappeared at g = 2.2 and existed in all samples [8]. Moreover,additional overlapping low magnetic field signals appeared indifferent samples. These lower magnetic field signals wereassumed to be attributed to the existence of strain betweennano-nickel particles [33,34].

We assume that the disappearance of this strain means thatnano-sized nickel particles are well separated among each others.In other words, the interaction between the metal and the supportis minimum. According to this assumption, one can observe easilyfrom the ESR spectra of the samples (Fig. 7) that, the freshlyprepared nickel catalyst supported on SA-1500 exhibits no strainand this means that the interaction between metal and the supportis minimum. XRD Diffractograms of the catalysts (Fig. 2) show alsothat it has the larger degree of crystallinity.

It is clearly shown from Fig. 7 that the particle size decreasesprogressively by increasing the number of use. A decrease of 30%after using the catalyst supported on SA-1500 was observed.Furthermore, the Ni phase turned into almost an amorphous phasewhich agreed well with the XRD investigation.

Moreover, using the calculation of particle size using Kawabataequation (labeled on each samples in Fig. 7), it can be observedthat, as the number of successive times of use of catalyst inhydrogenation reaction increases, the particle size of nickeldecreases. In other words, the amorphization of nickel is increasingwhich previously concluded from XRD diffractograms.

In contrast to the previous observation, the particle size of Ni inthe catalyst sample whose support was SA-500 seems to beincreasing after successive use. This indicates that the mode ofdeactivation of this catalyst sample may suffer also from some kind

5. Catalytic activity

The catalytic activity of catalyst samples under investigawas carried out by hydrogenation of PNP into PAP. This reacwas carried out using hydrazine hydrate as hydrogen dono80 8C. As being mentioned before, it seems that the express ofcatalytic activity as a time to reach 100% conversion being the bexpress. This is because the 100% conversion is accompanied byindicative change in color (green! colorless) which acts as aindicator for ending the reaction.

The catalytic activity of the bare supports calcined at 500, 1and 1500 8C (SA-500, SA-1000, and SA-1500) were examinedshowed no catalytic activity. Further 5 wt% Ni was loaded onprecalcined supports and reduced using Hydrazine hydrate at100 8C.

The loaded Ni-support catalysts were then examinedprementioned hydrogenation reaction.

Fig. 8 shows the time in seconds for 100% conversion afunction of calcination temperature of the support material.

It is clearly shown from Fig. 8 that the increase inprecalcination temperature of the support material within 51500 8C led to a progressive increase in the catalytic activity. Tbeing evidenced from the progressive significant decrease intime for attaining 100% conversion. This increase in the pcalcination temperature from 500 to 1500 8C decrease the tim100% conversion from 107 to about 70 s.

XRD investigation of the catalyst samples shows clearly thatincrease in calcination temperature of the SiO2–Al2O3 suppmaterial within 500–1500 8C much increase the degreecrystallinity of the phases present in the support. So, the increin crystallinity of the support material showed a paraprogressive increase in catalytic activity.

In order to make a comparison between the catalytic activitthe system investigated with the commercial catalyst (RaNickel), the hydrogenation reaction was carried out forcommercial sample under the same conditions and ratios useother samples. The time needed to obtain 100% conversattained 260 s instead of 69 s of the catalyst investigated whsupport was SA-1500. In other words the prepared catalyst show

Fig. 8. Catalytic activity of different catalysts expressed as time reaches to 1

conversion against calcination temperature of the support.


yst.redes)

.vitysive

of sintering.In order to eliminate the possibility of leaching of Ni metal from

the support during the hydrogenation reaction, elemental analysisfor nickel in supernatant was done after each experiment. Theresults showed that the amount of Ni leached in all samples wasvery small and can be neglected.

Please cite this article in press as: I.H.A.E. Maksod, et al., Synthesis anAl2O3, Appl. Surf. Sci. (2008), doi:10.1016/j.apsusc.2008.07.117

a catalytic activity about 4-fold than that of Raney nickel catalIn order to shed some light on the durability of the prepa

catalyst, the reaction was done several successive times (5 timand the effect of this parameter is readily illustrated in Fig. 9

It is clearly shown from this figure that the catalytic actisuffer slight decrease in its catalytic activity during the 3 succes



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. However, the 4th use of the catalyst whose support is SA-500most of its catalytic activity showing no measurable catalyticity in the 5th use. While the catalysts whose support are SA-

and SA-1500 lost some of their activity after 5th use. Theease was, however, more pronounced in case of catalyst samplese support is SA-1500. This finding suggested that the catalystse support calcined at 1000 8C is recommended for suchtion for its obvious durability.eturning to EDX results which showed the surface nickel in theple whose support is SA-500 decreases from fresh to 5th usedlyst as (10! 4 atomic%) (Table 1). Thus it can be concludednot all surface Ni atoms are catalytically active. In case of

lysts based on SA-1000 and SA-1500 supports, the durability isg higher than that of those based on SA-500 support. Thus,ough the sharp decrease was observed in the surface Ni atoms

number of active nickel species increases and hence catalyticactivity and durability increase. This may be because of that in caseof crystalline samples diffusion of the reactants into the bulk ismuch easier than that of the amorphous ones.

It seems that the change in surface concentration of Ni atoms asa function of calcination temperature of the support material mayhave a decisive role in changing the catalytic activity. This has beendone by following the change in the catalytic activity, expressed astime to reach 100% conversion, as a function of the differencebetween the surface Ni of the 5th used catalyst subtracted from thecalculated bulk concentration of Ni. The results obtained are givenin Fig. 10.

From this figure, it can be shown that the sample whose supportis SA-1000, has the lowest difference to the calculated bulk valuesafter 5 times of use. This may explain the highest durability of thissample.

This led us to assume that as the atomic percent of Ni approachesthe calculated bulk values, the catalytic activity reaches maximum.

The %atomic Ni after 5 times of using the nickel catalystsubtracted from calculated bulk atomic% of Ni loaded on SA-500,SA-1000 and AS-1500

6. Conclusions

The following conclusions can be drawn from this research:

1. Nickel loaded on SiO2–Al2O3 support being very effectivecatalyst in hydrogenation of p-nitrophenol to p-aminophenol.That it was attained 100% conversion in only 69 s instead of260 s for commercial Raney nickel. In addition the possibility ofreuse it more than one time with great efficiency give it anotheradvantage to commercial Rainey nickel which cannot be usedmore than one time.

2. The crystallinity of the support plays a very important role in thecatalytic activity of the nickel catalyst. The increase in theprecalcination temperature of the support material within 500–1500 8C increases the degree of crystallinity of the support andalso increases the catalytic activity of the catalyst.

3. The catalyst investigated showed high durability. The optimumdurability was attained at catalyst sample whose support isprecalcined at 1000 8C (SA-1000).

4. The mechanism of hydrogenation reaction is supposed accord-ing to the change in color during the reaction. Change in color inthe reaction make a self-indication of 100% conversion whichsave the time and effort for following up the reaction.

5. In comparison of our previous work with 5 wt% nickel catalystsupported on single oxides of SiO2 and Al2O3 [35], the nickelcatalysts supported on mixed oxides were proven to be higher inboth catalytic activity and durability than those catalystssupported on single oxides.

References

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0. The %atomic Ni after 5 times of using the nickel catalyst subtracted from

lated bulk atomic% of Ni loaded on SA-500, SA-1000 and AS-1500.

. The effect of successive times of using the nickel catalyst loaded on SA-500,

000 and AS-1500.


ng the reaction in case of both catalysts based on SA-1000 and500 supports (Table 1), the catalytic activity is being notted mainly. This leads us to conclude that in these samplessurface and bulk nickel participate in the reaction while in SA-sample only a part of surface nickel is activated. In other

ds, as the degree of the crystallinity of the support increases

ase cite this article in press as: I.H.A.E. Maksod, et al., Synthesis an


genation of Edible Oil, Ph.D. Thesis, Ain Shams University, 2005.[8] M.M. Selim, I.H. Abd El-Maksoud, Microporous Mesoporous Mater. 85 (2005) 273.[9] C.V. Rode, M.J. Vaidya, R. Jaganathan, R.V. Chaudhari, Chem. Eng. Sci. 56 (2001)

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